The general objective of this research is to study the role(s) of insulin and selected other hormones in the turnover of specific proteins in rat tissues. The specific purpose of the project is to study the role(s) of insulin, other hormones (e.g., cortisol, growth hormone, glucagon, and thyroxine), and energy sources (e.g., glucose, fructose and pyruvate) in the control of the turnover of glucose-6-phosphate dehydrogenase and malic enzyme in rat adipose tissue and liver and in the control of the degradation of actin and myosin in skeletal muscle. Techniques involving the prolonged incubation of adipose tissue, the use of insulin-sensitive isolated hepatocytes, and the perfused hindquarters of rats will be used in this project in an effort to provide more rigorous control of experimental factors than is possible in the whole animal. Immunochemical techniques will be used in an attempt to determine the manner in which insulin stimulates synthesis and inhibits degradation of G6PDH. Measuring the effects of insulin and other factors on the release of 3-methylhistidine from perfused rat hindquarters permits an estimation of the importance of a variety of agents on the rates of degradation of actin and myosin.